1. Field
One feature relates to determining spectrum availability in wireless communication systems, and more particularly, to a zone or grid based voting method to determine the usage of a frequency spectrum band or channel based on reports from user sensing devices.
2. Background
In some wireless networks, it may be beneficial for the network to determine which channels or bands of a frequency spectrum may be in use by others and therefore avoid such channels or bands. For example, in cognitive radio networks, primary signal information from sensing devices is reported to an information center (e.g., Base station). Then, based on the reports, the information center infers whether there exists a primary signal or not. If not, the information center sends a control signal to each device to use the spectrum band or channel since it is vacant. Otherwise, the information center and/or sensing devices refrain from using the spectrum band.
To disrupt normal service, an attacker can generate a fake primary signal or mask a primary signal. By faking the primary signal, an innocent user (device) may never be able to use an otherwise vacant spectrum band. On the other hand, by masking the primary signal, an unknowing device may start using the spectrum band thereby disrupting incumbent user (e.g., devices currently using the spectrum band). Hence, a voting scheme may be utilized to filter out the fake signals or masking. The simplest voting scheme is to gather all the sensing information (N) from each device and infer that there exist a primary signal if the number of primary signals (m) exceeds certain threshold (i.e., m/N>α).
Two prior art voting schemes include Simple Majority Voting and Absolute Majority Voting. The simple majority voting scheme is a form of voting where, given two options, the option receiving the most votes wins. Absolute majority voting is another form of voting scheme where the winner is the option that gets more than half of all possible votes including abstentions. In the cognitive radio network context, the two report options are: (1) primary signal exist or (2) primary signal does not exist.
Both of these prior art voting schemes are not appropriate for cognitive radio networks as they are susceptible to disruption and security risks by attackers. Consequently, a voting scheme is needed to determine whether a spectrum band is in use while mitigating the possibility of an attacker.